On Thu, Jan 19, 2017 at 1:51 PM, Joao Pinto <Joao.Pinto@xxxxxxxxxxxx> wrote:
> Às 7:16 PM de 1/19/2017, Linus Torvalds escreveu:
>> On Thu, Jan 19, 2017 at 10:54 AM, Joao Pinto <Joao.Pinto@xxxxxxxxxxxx> wrote:
>>>
>>> I am currently facing some challenges in one of Linux subsystems where a rename
>>> of a set of folders and files would be the perfect scenario for future
>>> development, but the suggestion is not accepted, not because it's not correct,
>>> but because it makes the maintainer life harder in backporting bug fixes and new
>>> features to older kernel versions and because it is not easy to follow the
>>> renamed file/folder history from the kernel.org history logs.
>>
>> Honestly, that's less of a git issue, and more of a "patch will not
>> apply across versions" issue.
>>
>> No amount of rename detection will ever fix that, simply because the
>> rename hadn't even _happened_ in the old versions that things get
>> backported to.
>>
>> ("git cherry-pick" can do a merge resolution and thus do "backwards"
>> renaming too, so tooling can definitely help, but it still ends up
>> meaning that even trivial patches are no longer the _same_ trivial
>> patch across versions).
>>
>> So renaming things increases maintainer workloads in those situations
>> regardless of any tooling issues.
>>
>> (You may also be referring to the mellanox mess, where this issue is
>> very much exacerbated by having different groups working on the same
>> thing, and maintainers having very much a "I will not take _anything_
>> from any of the groups that makes my life more complicated" model,
>> because those groups fucked up so much in the past).
>>
>> In other words, quite often issues are about workflows rather than
>> tools. The networking layer probably has more of this, because David
>> actually does the backports himself, so he _really_ doesn't want to
>> complicate things.
>
> I totally understand David' side! Synopsys is a well-known IP Vendor, and for a
> long time its focus was the IP only. Knowadays the strategy has changed and
> Synopsys is very keen to help in Open Source, namelly Linux, developing the
> drivers for new IP Cores and participating in the improvement of existing ones.
> I am part of the team that has that job.
>
> In USB and PCI subystems developers created common Synopsys drivers (focused on
> the HW IP) and so today they are massively used by all the SoC that use Synopsys
> IP.
>
> In the network subsystem, there are some drivers that target the same IP but
> were made by different companies. stmmac is an excelent driver for Synopsys MAC
> 10/100/1000/QOS IPs, but there was another driver made by AXIS driver that also
> targeted the QOS IP. We detected that issue and merged the AXIS specific driver
> ops to stmmac, and nowadays, AXIS uses stmmac. So less drivers to maintain!
>
> The idea that was rejected consisted of renaming stmicro/stmmac to dwc/stmmac
> and to have dwc (designware controllers) as the official driver spot for
> Synopsys Ethernet IPs.
> There is another example of duplication, which is AMD' and Samsung' XGMAC
> driver, targeting the same Synopsys XGMAC IP.
>
> I am giving this examples because although the refactor adds work for
> backporting, it reduces the maintenance since we would have less duplicated
> drivers as we have today.
This sounds as if the code in question would only receive backports
for a specific
time (determined by HW lifecycle, maintenance life cycle and such).
So I wonder if this could be solved by not just renaming but
additionally adding a
symbolic link, such that the files in question seem to appear twice on
the file system.
Then backports ought to be applicable (hoping git-am doesn't choke on symlinks),
and after a while once the there no backports any more (due to life
cycle reasons),
remove the link?
This also sounds like a kind of problem, that others have run into before,
how did they solve it?
Thanks,
Stefan
>
> Thanks,
> Joao
>
>
>> Linus
>>
>